Noob ?:any difference between AE Lock (*) and depressing shutter half-way?

[new2DSLR]

My appologies if this question has already been asked in the past...

I was wondering what the difference was between setting the AE lock with the "*" button and just holding down the shutter half-way, and recomosing, then shooting. I thought holding down the shutter half-way held the aperature/speed settings constant while you recomposed. So, why the need for AE Lock (*) button?

Any clarification on this would be greatly appreciated.

thanks,

Brian

[Cadwell]

AE lock locks exposure... (unless modified by custom functions) half holding the shutter release locks exposure AND focus....

[new2DSLR]

AE lock locks exposure... (unless modified by custom functions) half holding the shutter release locks exposure AND focus....

Thanks Cadwell! That clears things up a lot.

I'm wondering, wouldn't you usually want to focus lock on the subject you are AE locking? I'm thinking of the scenario where I'm taking a picture of a subject, but off to the side. In this case, I'd want the subject to be in correct focus (focus lock) and in correct exposure (AE lock), but just to the side.

In what situations would you want the subject to have the correct exposure, but the focus to be on something else (which may not have the correct exposure, since the exposure was locked prior)?

Sorry, just trying to learn.

thanks again,

Brian

[elbirth]

Brian, a lot of people (myself included) just find it more natural to separate the AE lock and focus lock just to have more control... plus everytime you hit the shutter button you're not risking messing up your focus.

The example I hear a lot is that keeping them separate is especially useful if you're doing some portrait photography and the person is walking around under some trees or something, but stays the same distance from you, roughly. You'll want to remain focused on the person, but if they walk into a spot where it's more sunny, you'll want to wait until you actually take the picture to set the exposure. By having focus on the * button, you can leave focus alone once set and let the shutter button set the exposure whenever you want to snap a shot. The same holds true for something like racing, where you're tracking a fast-moving car that may go in and out of areas with more/less sunlight. If you let the exposure get set when you lock focus, by the time you take the picture it might be in a spot where the picture will turn out over or under exposed.

[CyberDyneSystems]

I seocnd that.. set CF#4 to "1" and focus with the * button ;)

[Sathi]

I often use exposure lock. Usually to expose for the background. Most often it is the sky I am trying to get the correct exposure for, yet I still want good focus on a foreground subject. I will point the camera at the sky, lock exposure there, and then focus on something close.

[bigun]

I know that there is another thread dealing with "cf 4" but I wanted to 3rd CDS motion that it is a very good way of composing and locking focus seperatly from your exposure. I've been using it this way for about a week and love it!!

Bigun...

[new2DSLR]

Elbirth - thanks for the example on when one might need to separate AE lock / AF lock.

I read this thread over the weekend, and took your and CDS' advice and made CF#4=1 on my XT. One drawback I have encountered is difficulty keeping focus on a moving subject when using the (*) for AF lock. I was trying to take picture of my (rather active) two year old kid in a children's museum, and I found by the time I press the (*) for AF lock, then press the shutter, where I had originally locked the AF became irrelavant because the he moved. This was less of a problem with both the AF and AE lock were on the shutter release button.

Compounding to this problem was me setting aperature value high (2.8; am I supposed to say "setting the aperature value low"), making the slightest off-focus unforgiving (it was indoor, and I didn't want to use flash). I tried the AI Servo mode, but didn't fare much better (most probably due to my inexperience in this mode).

I will continue to try the * for AF lock for a while, but may want to switch back if I'm too slow to go from (*) to shutter release.

[R1 Kid]

I seocnd that.. set CF#4 to "1" and focus with the * button ;)

Plain and simple...No question, just do it.

[elbirth]

Elbirth - thanks for the example on when one might need to separate AE lock / AF lock.

I read this thread over the weekend, and took your and CDS' advice and made CF#4=1 on my XT. One drawback I have encountered is difficulty keeping focus on a moving subject when using the (*) for AF lock. I was trying to take picture of my (rather active) two year old kid in a children's museum, and I found by the time I press the (*) for AF lock, then press the shutter, where I had originally locked the AF became irrelavant because the he moved. This was less of a problem with both the AF and AE lock were on the shutter release button.

Compounding to this problem was me setting aperature value high (2.8; am I supposed to say "setting the aperature value low"), making the slightest off-focus unforgiving (it was indoor, and I didn't want to use flash). I tried the AI Servo mode, but didn't fare much better (most probably due to my inexperience in this mode).

I will continue to try the * for AF lock for a while, but may want to switch back if I'm too slow to go from (*) to shutter release.

for a situation like that, having it either way won't make too much difference (I'll admit, it does take a little getting used to by separating them). But put your camera into AI Servo mode and keep the * button held down while tracking your kid and it will continually refocus to keep the best focus... then just press the shutter button when you want to take a picture all while still holding the * button

[HJMinard]

for a situation like that, having it either way won't make too much difference (I'll admit, it does take a little getting used to by separating them). But put your camera into AI Servo mode and keep the * button held down while tracking your kid and it will continually refocus to keep the best focus... then just press the shutter button when you want to take a picture all while still holding the * button

In conjunction with elbirth's suggestion, consider changing C.Fn-04 from "1" to "3". This retains the focus on the "*" button and the exposure on the shutter button, but it removes the AE lock and thus with a moving subject the exposure will not be set until the exact moment the shutter is activated. Very useful if your subject is moving in and out of shadows.

[elbirth]

In conjunction with elbirth's suggestion, consider changing C.Fn-04 from "1" to "3". This retains the focus on the "*" button and the exposure on the shutter button, but it removes the AE lock and thus with a moving subject the exposure will not be set until the exact moment the shutter is activated. Very useful if your subject is moving in and out of shadows.

does that work if you press the shutter but only let it back up to a half-press, or do you have to fully depress the shutter button after taking a picture? Also, does that allow you to track a subject while half-pressing and still have the exposure not get locked until the picture is actually taken?

[HJMinard]

does that work if you press the shutter but only let it back up to a half-press, or do you have to fully depress the shutter button after taking a picture? Also, does that allow you to track a subject while half-pressing and still have the exposure not get locked until the picture is actually taken?

I'm not sure I'm following your first question ... but I know that with this setting a half-press never locks the exposure. According to the manual, the "exposure is set at the moment the picture is taken". A half-press provides meter readings, but still the exposure is never "locked" until the shutter is activated. So I think the answer to your first question is it will work either way.

The answer to your second question is yes ... with C.Fn-04-3 you can track while half-pressing and the exposure will not be set until the picture is taken.

[elbirth]

yeah, that answers my question, thanks :)

[new2DSLR]

... But put your camera into AI Servo mode and keep the * button held down while tracking your kid and it will continually refocus to keep the best focus... then just press the shutter button when you want to take a picture all while still holding the * button

Oh, I wasn't aware I can hold down the (*), or for that matter, press the shutter release while holding down the (*)--I was pressing the (*) once, and then letting it go. Thanks Elbirth, I'll try this on my next shoot.

Brian

[new2DSLR]

I often use exposure lock. Usually to expose for the background. Most often it is the sky I am trying to get the correct exposure for, yet I still want good focus on a foreground subject. I will point the camera at the sky, lock exposure there, and then focus on something close.

Sathi, when you AE lock on the sky, don't you risk underexposing your subject (I assuming the sky is bright in comparison to the subject you finally set your focus to).

[chtgrubbs]

Locking the focus may not be such a good idea in some circumstances. Check this out:
http://visual-vacations.com/Photography/focus-recompose_sucks.htm

It might be better to lock exposure without locking focus.

[Loaded]

great thread lots of working info here

[prime80]

Locking the focus may not be such a good idea in some circumstances. Check this out:
http://visual-vacations.com/Photography/focus-recompose_sucks.htm

It might be better to lock exposure without locking focus.

Very interesting...

[KennyG]

The same holds true for something like racing, where you're tracking a fast-moving car that may go in and out of areas with more/less sunlight. If you let the exposure get set when you lock focus, by the time you take the picture it might be in a spot where the picture will turn out over or under exposed.

I'll dispute that. I don't know one motorpsort photographer that uses it that way. It is too awkward and the change in light is something we work with, taking the shot at the spot we want to. Great for static subjects, but holding down that button for the length of time we would have to is simply not practical.

[elbirth]

I'll dispute that. I don't know one motorpsort photographer that uses it that way. It is too awkward and the change in light is something we work with, taking the shot at the spot we want to. Great for static subjects, but holding down that button for the length of time we would have to is simply not practical.

consider me corrected, then. I don't shoot motor sports, so I have no personal experience with it, though it seems to me that you'd get better (more accurate) results if you tracked the car with your focus, rather than pre-determining a spot and risk having it out of focus if it doesn't drive to exactly the spot you're aiming for.....
similarly, having flexibility in setting the exposure seems like it'd be a plus

[I Simonius]

I'm not sure I'm following your first question ... but I know that with this setting a half-press never locks the exposure. According to the manual, the "exposure is set at the moment the picture is taken". A half-press provides meter readings, but still the exposure is never "locked" until the shutter is activated. So I think the answer to your first question is it will work either way.

The answer to your second question is yes ... with C.Fn-04-3 you can track while half-pressing and the exposure will not be set until the picture is taken.

But what about the problem where if the shutter is half held down for over 4 secs there will be a response delay unless you press the shutter again before you shoot??

Just came across that yesterday and it explained why there is sometimes a lag that I hadn't grokked

[muscleflex]

Wouldn't pressing the * to AE lock just the same as pressing the shutter halfway (for the Custom Functions) to AE lock? you're basically switching the buttons around with the custom functions?!

[new2DSLR]

While on the subject of custom functions, specifically CF#4, can anyone tell me if I'm interpreting CF#4=2 correctly?

According to the manual, CF#4=2 equates to AF for button, and AF lock (no AE lock) for half- shutter press.

My interpretation is as follows:
- If in "AI Servo" mode, the button acts as "AI-Servo" focus (that is, it's constantly focusing the moving subject), and the half-shutter press act as "one-shot" focus (focus lock).
- If in "One-shot" mode, both and the half-shutter press act the same way--"one-shot" focus (focus lock).

Am I interpreting this correctly?

Brian

[HJMinard]

Wouldn't pressing the * to AE lock just the same as pressing the shutter halfway (for the Custom Functions) to AE lock? you're basically switching the buttons around with the custom functions?!

No, not just switching buttons. The important change with CF-04 is that you're separating focus and exposure, whereas they're combined by default on one (shutter) button.

[muscleflex]

yes, but if you AE lock on something and then go back to where you want to focus - isn't it the same as you pressing the shutter halfway to ae lock and then going back to the part of the image then pressing the * to trigger the focus?

i'm just saying because i tried this and it's not for me - reason being my thumb doesn't lie on the * button by default..so it makes it hard for me to concentrate on placing my thumb on the * when i hold the camera. it's not the neutral position for my thumb! mind you, i have small hands! i'm a gymnast so i'm tiny! :-)

[jimbloomfield]

Kenny are you saying that you use the "*" for focus and the the shutter for AE and taking the actual photo? What CF do you have set?